1. Field of the Invention
This invention relates generally to a mechanical oscillator in a micro-electromechanical system (MEMS), which is of particular interest in radio frequency filters and oscillators, motion and pressure sensors, and charge detectors, chemical sensors, magnetic resonance force microscopes, and torque magnetometers. Mechanical oscillators within these devices are most often the central component. The instant invention is a high Q monolithic mechanical oscillator with ultra high sensitivity and ultra low energy consumption.
2. Description of the Related Prior Art
Mechanical oscillators based on silicon nanofabrication technology are used in a variety of applications including sensor devices (See R. D. Biggar and J. M. Parpia, “High-Q Oscillator Torque Magnetometer,” Rev. Sci. Instr. Vol. 69, 10, October 1998, 3558-3562 and See A. N. Cleland and M. L. Roukes, “Nanometerscale Mechanical Electrometer,” Nature, Vo. 392, Mar. 12, 1996, pp. 160-162.) In order to develop better micro mechanical oscillator systems, it is necessary to control the flow of mechanical energy out of the oscillator into the surroundings in order to increase the quality factor of the oscillator (Q) and to control the coupling of the oscillator to other devices. Very high Q's have been achieved for some modes of double paddle oscillators (See Kleinman et al., “Single Crystal Silicon High-Q Torsional Oscillators,” Rev. Sci Instrum. Vol. 56, pp 2088-2091, 1985.) The highest reported Q of about 2×109 is measured for a silicon oscillator at 3.5 K at a frequency of 5.1 kHz. The inverse Q or damping factor has been shown to increase as the temparture is raised above 20 K (See D. F. McGuigan et al., “Measurements of the Mechanical Q of Single Crystal Silicon at Low Temperatures,” J.Low Temp. Phys., Vol. 30, pp 621-629. Energy losses remain a problem in these prior art systems especially when the oscillator is fabricated from a single substrate material and is of monolithic construction.